Embodiments of the present invention relate to a wafer and a method for forming the same, and more specifically, to a technology for separating each chip from a wafer including a plurality of chips.
A radio frequency identification (RFID) tag chip has been widely used to automatically identify objects using a radio frequency (RF) signal. In order to automatically identify an object using the RFID tag chip, an RFID tag is first attached to the object to be identified, and an RFID reader wirelessly communicates with the RFID tag of the object in such a manner that a non-contact automatic identification scheme is implemented. With the widespread use of RFID technologies, the shortcomings of related automatic identification technologies, such as barcode and optical character recognition technologies have been greatly reduced.
In recent times, the RFID tag has been widely used in physical distribution management systems, user authentication systems, electronic money (e-money), transportation systems, and the like.
For example, a physical distribution management system generally performs classification of goods or management of goods in stock using an Integrated Circuit (IC) recording data therein, instead of using a delivery note or tag. In addition, a user authentication system generally performs an Entrance and Exit Management function or the like using an IC card including personal information or the like.
In the meantime, a non-volatile ferroelectric memory may be used as a memory in an RFID tag.
Generally, a non-volatile ferroelectric memory, (i.e., a Ferroelectric Random Access Memory (FeRAM)) has a data processing speed similar to that of a Dynamic Random Access Memory (DRAM), and preserves data even when power is turned off, and thus many developers are conducting intensive research on FeRAM as a next generation memory device.
The above-mentioned FeRAM has a very similar structure to that of DRAM, and uses a ferroelectric capacitor as a memory device. The ferroelectric substance has high residual polarization characteristics such that data is not lost although an electric field is removed.
A RFID device uses frequencies of various bands. In general, as a frequency band is decreased, the RFID device has a lower recognition speed, is operated at a shorter distance, and is less affected by the surrounding environment. In contrast, as a frequency band is increased, the RFID device has a higher recognition speed, is operable at a relatively longer distance, and is more susceptible to the surrounding environment.
A plurality of RFID chips are included in a wafer. The RFID chips are arranged in rows and columns. In order to perform dicing of each RFID chip at a wafer level, laser sawing may be used.
In addition, mask align keys, are formed on a scribe line of a wafer. The mask align keys are used as a reference for separating individual RFID chips from one another. In other words, the scribe line is cut by a laser beam such that individual RFID chips can be separated from one another. The cutting process requires much time and thus increases production costs.
Also, since a conventional RFID device needs to have a mask align key on a scribe line, a relatively large interval should be secured between chips. In other words, one scribe line for separating each chip and another scribe line for align keys are widely arranged at a given interval among chips. As a result, the number of net dies per wafer is decreased.